The blood group characteristic in humans is controlled by three set of alleles, namely, `I^(A), I^(B), and i. ` The alleles, `I^(A) and I^(B)`, are equally dominant whereas allele, i, is recessive to the other alleles. The individuals with genotype, `I^(A) I^(A) and I^(A) i`, have blood group A whereas the individuals with genotype, `I^(B) I^(B) and I^(B) i`, have blood group B. The persons with genotype `I^(A) I^(B)` have blood group AB while those with blood group O have genotype ii.
Hence, if the father has blood group A and mother has blood group B, then the possible genotype of the parents will be
Father Mother `I^(A) I^(A)` or `I^(A) i I^(B) I^(B)` or `I^(B) i`
A cross between homozygous parents will produce progeny with AB blood group.
